The objective of the proposed line of research is to discover neuromuscular goals of the able-bodied ankle-foot system for walking and apply them toward the design of more biomimetic ankle-foot prostheses and orthoses. These goals will also assist in the evaluation of existing assistive or replacement devices for disabled or amputated ankle-foot systems. [unreadable] [unreadable] Able-bodied persons will walk and stand with shoes having rockers of different radii to examine the response of the ankle (and the rest of the body) to changes in these rockers. The investigators hypothesize that subjects in the study will change their ankle movements during walking in a way that provides a similar circular effective rocker shape (roll-over shape) of the ankle, foot, and shoe system. During standing and fore-aft swaying, the ankle-foot-shoe system is expected to provide a flat effective rocker for stability and this flat rocker is expected to remain the same with all shoe conditions. [unreadable] [unreadable] If the investigators' hypotheses are supported, prostheses with simple ankle locking and unlocking mechanisms could be developed to provide a more stable base to users during standing activities (locked ankle joint) and allowing the ankle-foot system to conform to an appropriate roll-over shape during walking (unlocked ankle joint). [unreadable] [unreadable] [unreadable]